How can astronomers tell whether a black hole exists in the center of a galaxy?

Answer 1

Astronomers believe there may be a black hole at the center of our galaxy because of a compelling body of evidence supporting the idea. Recent observations of the behavior of stars at the center of our Milky Way show them orbiting an object which, based on the stars' velocities, indicates its gravitation pull on them is caused by an object something that weighs in the vicinity of four million solar masses. The point of the nearest approach (perigee) in the orbit of the closest of these stars misses it at a distance which sets the upper limit of the size of the object. Given that nothing else in our physical theory could be so small yet so massive, the best fit is a supermassive black hole.

Answer 2

Astronomers can detect a black hole's presence in the center of a galaxy by observing stars and gas orbiting around an invisible central point, showing the influence of a massive object. They can also study the emission of radiation and energy coming from the region, along with detecting gravitational waves produced by the black hole's activity.

Answer 3

Hawking Radiation would be one of the newer ways to detect black holes. Other than this, the only other way to detect a black hole is from the effect on its surroundings.